Okay, this going to be quite the post, kids.
One day, Pink Guy plays a game of rock-paper-scissors wtih his friend, Red Dick. Red Dick loses, and turns to Prometheus (the big musclebound briefs-only mo-facka). Prometheus proceeds to chase Pink Guy down and attack with a trashbin. Pink guy is hurt, and asks ChinChin for help. Chinchin beats up Red Dick, but is also beaten by Prometheus.
The point where Franku starts giving sacrifices is unclear to me. All we know is that Chin Chin is a) much more powerful than Franku, and Franku is virtually powerless compared to Chin Chin and; b) Chin Chin has been demanding sacrifices for a while now from possibly everyone in the Frankiverse (except from the Peace^Lords) including Franku.
Onr day Franku misses a sacrifice, and has angered ChinChin at this point. He takes Salamander Man hostage until Franku finds enough sacrifices (from his fans). Franku goes to the realm Chin Chin is in, and sends Pink Guy to warn the civilians of Chin Chin's presence in their realm. Franku offers all the sacrifices (i.e. the ChinChin Sacrifice 2014) but forgets to bring his own sacrifice. After being shown Salamander Man's assflute ability, he lets Franku pass because "Salamander man's assflute is too good".
Fast-forward to 2015, when Chin Chin starts whispering and appearing in and out of videos once more and tension is teetering on the edge. Franku once more gathers all his fans for more sacrifices, but now he has a much larger price to pay. At this point ChinChin desires Pink Guy. Franku denies Chin Chin's demand, and is banished to the Rice Fields. Salamander Man finds Franku, and gives him companionship until he tells Salamander Man to go back to the original world (i.e. our world). Meanwhile, Pink Guy and Red Dick, moping over the loss of their one true b0ss, tried cooking some food. A mysterious Franku pops in and comments on the scent of their food. Pink Guy suspects that this Franku (wearing shades and sometimes an aeronautical cap) is an impostor, possibly Chin Chin in disguise. Red Dick disappears, nowhere to be found.
[The following is not really lore, as stated in FF's video] Pink Guy starts travelling through Realm 8 looking for Franku. He encounters Green Cunt, who then proceeds to assault him. Pink Guy is saved by Salamander Man. Pink Guy gives him a CD of all the Chin Chin Sacrifices for 2016. They conspire to meet at certain coordinates on the day ChinChin is expected. Salamander Man and Pink Guy walk away after that.
That's all for the core lore of the FilthyFrank universe. Any other lore videos don't exactly contribute to the progression of the story. If you want to know more, check out the FilthyFrank Wikia page. The Dark Lord knows it can explain a lot more than I can.